Exchange Surfaces

Question 1

Describe how diffusion distance, SA, Volume, and SA: Volume ratio vary with increasing organism size.

Answer 1

• As organism gets bigger, all dimensions increase.
• Diffusion distance by a linear factor, SA by a factor of^2 and volume by a cubed factor.
• This means that volume increases faster than SA so the SA: Volume ratio decreases.

Question 2

Describe how the level of activity of an organism is related to demand for oxygen and glucose.

Answer 2

As activity increases, the demand for energy increases. This requires a higher rate of respiration and therefore a higher demand for oxygen and glucose.

Question 3

Explain how volume is related to demand and surface area is related to supply and how this means adaptations are required in larger organisms.

Answer 3

• Larger volumes require more oxygen and glucose as they have many more respiting cells.
• Exchange takes place across surfaces so larger surface area increases the ability to supply.
• In organisms with larger volumes, simple surface area is not adequate to meet the demand of the cells so adaptations occur in order to increase surface area, and to have large exchange surfaces.

Question 4

Suggest some reasons why some organisms need specialised exchange systems.

Answer 4

• Larger volumes so SA:Vol ratio is too small to meet demand.
• High activity levels

Question 5

State the 4 features of efficient exchange surfaces. For each feature, explain how it increases efficiency of the exchange surface.

Answer 5

1. Large surface area: Overcomes SA:Vol problems.
2. Thin: Short diffusion distance.
3. Well ventilated: Helps maintain a concentration gradient.
4. Good blood supply: Helps maintain a steep concentration gradient.

Question 6

State Fick’s Law and show how the importance of each of the 4 features of efficient exchange surfaces can be explained by his law.

Answer 6

• Rate of diffusion is proportional to (SA x concentration gradient)/Thickness of barrier.
• Ventilation and blood supply affect concentration gradient.

Question 7

Describe the structure of the nasal cavity and how it is adapted to its function.

Answer 7

• Large surface area with good blood supply warming gases to same temperature as inside the lungs.
• Hairy lining which secretes mucus to trap dust/bacteria, and protect the delicate lining of the lungs.
• Moist to increase humidity and reduce evaporation from exchange surfaces.

Question 8

Describe the structure of trachea/bronch/large bronchioles and how it is adapted to its function.

Answer 8

• Cartilage rings to stop collapsing.
• Cilla and mucus to trap dust etc. and sweep up and out.
• Smooth muscle + elastic fibres to allow tube size to change — wider for more oxygen, smaller to reduce chance of infection.

Question 9

Describe the structure of the smaller bronchioles and how it is adapted to its function.

Answer 9

• Smooth muscle and elastic fibres.
• Squamous epithelium — some gas exchange occurs.

Question 10

Describe the importance of elastic fibres in the function of alveoli.

Answer 10

They spring back when you breathe out to push air depleted in oxygen out.

Question 11

Describe the importance of lung surfactant in the function of alveoli.

Answer 11

It reduces surface tension, stopping the walls of the alveoli sticking together.

Question 12

Explain how the mammalian gaseous exchange system is adapted to be an efficient gas exchange surface.

Answer 12

1. Large surface area (alveoli)
2. Short distance
3. Good blood supply (network of capillaries)
4. Ventilated

Question 13

Define ‘breathing’

Answer 13

The physical process of inhaling oxygen and exhaling carbon dioxide

Question 14

Define ‘ventilation’

Answer 14

The flow of air in and out of lungs.

Question 15

Define ‘gas exchange’

Answer 15

The diffusion of oxygen and carbon dioxide between the alveoli and the blood.

Question 16

Define ‘inspiration’

Answer 16

Breathing in, inhalation

Question 17

Define ‘expiration’

Answer 17

Breathing out, exhalation

Question 18

Define ‘active process’

Answer 18

Uses energy for muscle contraction.

Question 19

Define ‘passive process’

Answer 19

Relaxing of muscles

Question 20

Describe the process of inspiration linking the action of muscles, movement of structures, the change in pressure within the lungs, and the direction of airflow.

Answer 20

• External intercostal muscles and diaphragm contract.
• Ribs move up and out, diaphragm flattens.
• Volume in lungs increases.
• Pressure in lungs decreases.
• Pressure in lungs is lower than atmospheric pressure.
• Flow of air into lungs.

Question 21

Describe the process of normal expiration linking the action of muscles, the movement of structures, the change in pressures within the lungs, and the direction of airflow.

Answer 21

• External intercostal muscles and diaphragm relax.
• Ribs move down and in, diaphragm becomes domed.
• Volume in lungs decreases.
• Pressure in lungs is higher than atmospheric pressure.
• Flow of air out of lungs.

Question 22

Describe how the process of forced expiration is different from normal expiration and suggest when it might be used.

Answer 22

• Internal intercostal muscles contract using energy (active process) forcing the rib cage down and in, and decreasing the volume in lungs.
• Used to blow out a candle etc.

Question 23

State 3 pieces of equipment used to measure the functioning of the lungs. For each outline how they work.

Answer 23

1. Peak flow maters — measure maximum rate at which air can be expelled from the lungs.
   2.Vitalographs — peak flow meters that calculate and graph the volume of air expelled as you breath out as quickly as you can. Once meausre used to assess lung function is ‘forced expiratory volume in 1 second’ (FEV1).
2. Spirometers — floating chambers on water with a pivot so that it moves down when you inhale and up when you exhale, connected to a recording pen which draws a trace on a rotating drum.

Question 24

Outline how peak flow meters work.

Answer 24

• They measure the maximum rate at which air can be expelled from lungs.

Question 25

Outline how vitalographs work.

Answer 25

• They are peak flow meters that calculate and graph the volume of air expelled as you breath out as quickly as you can.
• One measure used to assess lung function is ‘forced expiratory volume in 1 second (FEV1).

Question 26

Outline how spirometers work.

Answer 26

• They are floating chambers on water with a pivot so that it moves down when you inhale and up when you exhale.
• They’re connected to a recording pen which draws a trace on a rotating drum.

Question 27

Describe how a spirometer measures change in lung volume and explain why it cannot measure absolute lung volume.

Answer 27

• It can calibrate trace for a known volume of air.
• It cannot ever completely empty lungs as there is always some residual volume that is not measured.

Question 28

Define ‘tidal volume’

Answer 28

The volume of air moved into or out of the lungs in one breath during normal breathing (in dm^3.breath^-1).

Question 29

Define ‘vital capacity’

Answer 29

• The volume of air breathed out after the deepest inspiration.
• It is the maximum volume of air that can be exchanged in one breath.

Question 30

Define ‘inspiration reserve volume’

Answer 30

The maximum extra volume that can be inhaled after normal inspiration.

Question 31

Define ‘expiratory reserve volume’

Answer 31

The maximum extra volume that can be exhaled after normal expiration.

Question 32

Define ‘residual volume’

Answer 32

The volume of air remaining in the lungs after a maximal expiration.

Question 33

Define ‘total lung capacity’

Answer 33

The volume in the lungs at maximal inspiration.

Question 34

Define ‘total lung capacity’

Answer 34

The volume in the lungs at maximal inspiration.

Question 35

Define ‘breathing rate’

Answer 35

The number of breaths per minute.

Question 36

Define ‘ventilation rate’

Answer 36

The volume oof air moved into and out of the lungs per minute.

Question 37

Explain how a spirometer trace is different to a graph of the changes in lung volume during breathing.

Answer 37

• The spirometer tranche doesn’t always show the residual volume and therefore doesn’t show the total lung capacity.
• Inspiration and expiration are the opposite way up as floating camber moves down as the lung volume increases, not up.

Question 38

Write an equation linking ventilation rate, breathing rate, and tidal volume.

Answer 38

Ventilation rate = breathing rate x tidal volume

Question 39

Describe how a spirometer trace would differ during exercise as compared to the trace before exercise started.

Answer 39

Peaks/troughs larger and closer together.

Question 40

Describe how tidal volume and breathing rate link to oxygen uptake and explain the importance of the change in tidal volume and breathing rate during exercise.

Answer 40

• Increased tidal volume and breathing rate means more air, and therefore more oxygen is entering the lungs and is available to be taken by the RBCs.
• During exercise, more oxygen is needed for respiration so uptake more air which must enter/leave the lungs at a faster rate.

Question 41

Define ‘exoskeleton’

Answer 41

An external skeleton of some organisms e.g. insects.

Question 42

Define ‘spiracle ’

Answer 42

• Small openings along the thorax and abdomen of an insect that opens and closes to control the amount of air moving in/out of the gas exchange system, and the level of water loss from the exchange surfaces.

Question 43

Define ‘tracheae’

Answer 43

The larger tubes of the tracheal system. They are held open by rings of chitin.